Cobra AF251-D003

The introduction of new materials and manufacturing processes continues to push the envelope of the structural complexity of the components found in modern propulsion systems and other critical aerospace technologies. To ensure the safe and cost-effective operation of these systems, their fracture-critical components must be inspected for the presence of damage at the end of the manufacturing process and often during service.  However, the current nondestructive testing (NDT) technology available to detect flaws in metallic components is not ready to address the full spectrum of complex-shape parts that are of practical interest today.  This represents a major technology gap which requires urgent attention. Recently, an innovative approach that combines the remarkable physicochemical properties of polycrystalline ice with the versatility of ultrasonic testing (UT) has been proposed as a possible solution, leading to what is now referred to as Cryo-ultrasonic testing (Cryo-UT). The underpinning idea of Cryo-UT is to transform a complex-shape part into a solid block by encapsulating the part in ice.  The ice block, and the component within it, can then be inspected by scanning an ultrasonic probe over the ice surface.  At the end of the inspection, the component can be retrieved by simply melting the ice.  Compared to conventional immersion UT, ice offers enhanced transmission of ultrasonic wave energy into the material of the component and therefore increases sensitivity to internal flaws.  To date, Cryo-UT research has focused on addressing fundamental scientific questions within laboratory settings.  As a result, current demonstrations of Cryo-UT have been limited to idealized specimen geometry and internal flaws.  In particular, the specimens have been limited to a size scale smaller than 7 inches and included canonical shapes like plates, pipe walls, domes, and spheres.  This proposal aims at accelerating the transition of Cryo-UT from the lab to industry. Specifically, it proposes to address critical questions about the practicality of Cryo-UT inspections in the presence of large aerospace components and the level of sensitivity that can be achieved.  R&D tasks are proposed to upscale the hardware technology required to encapsulate large engine components in ice and to optimize the sensitivity of ultrasonic measurements.  The end goal is to provide a demonstration of the feasibility of Cryo-UT by testing: (1) a high pressure turbine disk made from a dense alloy and with a diameter of 24 inches or more, and (2) a component containing internal structures and fabricated with additive manufacturing processes.